N52 alternator light

[hoveringuy]

One of the small details of the swap is that the N52 has a CAN controlled alternator. No more voltage regulator, no more second set of alternator windings that triggers the dashboard "ALT" light when the output fails.

Modern cars just have that light controlled by the ECU along with everything else.

How to make our old-fashioned light work when there's no connection for it on the alternator??

I made a simple circuit last winter and I've basically forgotten about it because it works so well, but time to commit it to CAD and order some adult versions of it.

The prototype was just gobs of solder and some components, but it works great!! The circuit works by creating a 5V reference voltage, and then using a voltage divider to feed a proportion of the IGN voltage into the other side of a comparator. If the voltage is below about 12 the ALT light is triggered, if it's above that it's not. My ALT light will extinguish a few seconds after the engine starts and come back on right after it turn off. It's adjustable so that if you have some big amps or massive headlights the voltage sag can be compensated for. I'll make a bunch of these and give one to anyone that has a completed N52 swap.

It's small enough that it just hides under the C101 plug boot.

[projectJTv4]

So much awesome in this post!

[TobyB]

So much analog in this post.

t
what, no microprocessor?

[hoveringuy]

So much analog in this post.

t
what, no microprocessor?

I mean, eventually it could capture CAN from the ECU to turn it on-off like it's meant to. In fact, my MK60 ABS has a little circuit that captures CAN traffic to illuminate the ABS light in the same manner.

I also had an earlier version of this circuit that was just two transistors and leveraged the fact that a transistor has a very definite forward bias voltage to turn it on-off, but it wasn't "crisp". When the transistor wasn't fully saturated it was just "kinda on" which wasn't satisfying.

[hoveringuy]

First prototype works, but I've made a bunch of small changes and placed an order for 50 revised boards, so get busy! The final version will have more SMD components, be slightly smaller yet.

[hoveringuy]

Final version. Shrunk down a bit more with additional SMD components, including some annoyingly small resistors. I have 10 completed and another 40 circuit boards, so basically a lifetime supply. I'll send one to whoever completes an N52 swap, courtesy of Seattle Circuit (I also have the OG fuel correction circuit in stock)

[Striker01]

Love the N52 Powa!!